Fail InstallAndroidDependencies cleanly when ResolveAndroidTooling has no resolved SDK

src/Xamarin.Android.Build.Tasks/Tasks/ResolveAndroidTooling.cs

@@ -90,11 +90,17 @@ public override bool RunTask ()
 				AndroidApiLevel = GetMaxStableApiLevel ().ToString ();
 			}
 
+			var androidSdk = MonoAndroidHelper.AndroidSdk;
+			if (androidSdk == null || AndroidSdkPath.IsNullOrEmpty ()) {
+				Log.LogCodedError ("XA5300", Properties.Resources.XA5300_Android_SDK);
+				return false;
+			}
+
 			string toolsZipAlignPath = Path.Combine (AndroidSdkPath, "tools", ZipAlign);
 			bool findZipAlign = (ZipAlignPath.IsNullOrEmpty () || !Directory.Exists (ZipAlignPath)) && !File.Exists (toolsZipAlignPath);
 
-			var lintPaths = MonoAndroidHelper.AndroidSdk.GetCommandLineToolsPaths (CommandLineToolsVersion ?? "")
-				.SelectMany (p => new[]{
+			var lintPaths = androidSdk.GetCommandLineToolsPaths (CommandLineToolsVersion ?? "")
+				.SelectMany (p => new [] {
 					p,
 					Path.Combine (p, "bin"),
 				});
@@ -107,7 +113,7 @@ public override bool RunTask ()
 				}
 			}
 
-			foreach (var dir in MonoAndroidHelper.AndroidSdk.GetBuildToolsPaths (AndroidSdkBuildToolsVersion ?? "")) {
+			foreach (var dir in androidSdk.GetBuildToolsPaths (AndroidSdkBuildToolsVersion ?? "")) {
 				Log.LogDebugMessage ("Trying build-tools path: {0}", dir);
 				if (dir == null || !Directory.Exists (dir))
 					continue;

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Tasks/ResolveSdksTaskTests.cs

@@ -219,5 +219,36 @@ public void ResolveSdkTiming ()
 			Directory.Delete (Path.Combine (Root, path), recursive: true);
 		}
 
+		[Test]
+		public void ResolveAndroidToolingWithMissingResolvedSdkDoesNotThrow ()
+		{
+			var path = Path.Combine (Path.GetTempPath (), "xa-tests", nameof (ResolveAndroidToolingWithMissingResolvedSdkDoesNotThrow), Guid.NewGuid ().ToString ("N"));
+			Directory.CreateDirectory (path);
+			var errors = new List<BuildErrorEventArgs> ();
+			var originalAndroidSdk = MonoAndroidHelper.AndroidSdk;
+			try {
+				MonoAndroidHelper.AndroidSdk = null;
+				IBuildEngine engine = new MockBuildEngine (TestContext.Out, errors);
+				var androidTooling = new Xamarin.Android.Tasks.ResolveAndroidTooling {
+					BuildEngine = engine,
+					AndroidSdkPath = path,
+					AndroidSdkBuildToolsVersion = "36.0.0",
+					TargetPlatformVersion = "37.0",
+					AotAssemblies = false,
+					SequencePointsMode = "None",
+					AndroidApplication = true,
+				};
+
+				Assert.IsFalse (androidTooling.Execute (), "ResolveAndroidTooling should fail when SDK resolution has not succeeded.");
+				Assert.AreEqual ("37", androidTooling.AndroidApiLevel, "AndroidApiLevel should still be calculated for dependency resolution.");
+				Assert.IsTrue (errors.Any (e => e.Code == "XA5300"), "XA5300 should be logged when Android SDK tooling is unavailable.");
+				Assert.IsFalse (errors.Any (e => e.Code == "XARAT7001"), "ResolveAndroidTooling should not throw when AndroidSdk is unavailable.");
+			} finally {
+				MonoAndroidHelper.AndroidSdk = originalAndroidSdk;
+				if (Directory.Exists (path))
+					Directory.Delete (path, recursive: true);
+			}
+		}
+
 	}
 }